1. Field of the Invention
The present invention relates to a semiconductor device and a method for manufacturing the same, and more specifically to a metal plug electrode used in a semiconductor device and a method for forming the same.
2. Description of Related Art
In a method for forming an electrode or an interconnection composed of titanium silicide film, in a semiconductor device, an example of the method for connecting between a polysilicon layer and a titanium nitride plug will be described with reference to FIGS. 1A and 1B.
As shown in FIG. 1A, an insulator film 2 is formed on a silicon substrate 1 in which various semiconductor circuit elements (not shown) are formed. A silicon conductive layer 1A formed in a surface region of the silicon substrate 1 constitutes a portion of one of the semiconductor circuit elements. A contact hole 3 is formed to penetrate through the insulator film 2 and to reach the surface of the silicon conductive layer 1A. A titanium film 4 is formed at a bottom of the contact hole 3, to contact with the surface of the silicon conductive layer 1A and furthermore, a titanium nitride film is formed to fill up the contact hole 3 and to cover the insulator film 2. Thereafter, the titanium nitride film is removed from the planar upper surface of the insulator film 2, so that a titanium nitride plug 5 filling up the contact hole 3 is formed.
Then, as shown in FIG. 1B, a polysilicon electrode 6 doped with a predetermined impurity is formed on the insulator film 2 and the titanium nitride plug 5.
However, the above mentioned prior art metal plug electrode is disadvantageous in that the contact resistance between the polysilicon electrode 6 and the titanium nitride plug 5 is large, and therefore, a stable operation of the semiconductor device and a high yield of production cannot be obtained.